Fluorinated pyrimidine anti-cancer agents including 5-fluorouracil (5-FU) are representative anti-cancer agents frequently used for malignant tumors such as breast cancer, gastrointestinal cancer and the like. It is known, however, that administration of a fluorinated pyrimidine anti-cancer agent to a patient genetically defective in dihydropyrimidine dehydrogenase (DPD), which is a rate-determining enzyme in fluorinated pyrimidine decomposition, raises blood concentration of fluorinated pyrimidine, as well as causes serious side effects such as blood disorder, bone marrow suppression and the like, which could lead to death in the worst case. Since DPD is an enzyme that generally degrades uracil and thymine, DPD-defective patients are known to show high concentrations of uracil and thymine, particularly uracil, in urine or blood. Therefore, quantification of the concentration of uracil in urine or blood of patients before administration of a fluorinated pyrimidine anti-cancer agent to the patients enables diagnosis of DPD deficiency, based on which an accident due to the administration of a fluorinated pyrimidine anti-cancer agent to DPD defective patients can be prevented.
As a method of quantifying uracil in urine or blood, a method using high performance liquid chromatography (HPLC) (S. Sumi, K. Kidouchi, S. Ohba and Y. Wada, J. Chromatogr. B 1995, 672, 233-239), and an immunological measurement method using an anti-uracil monoclonal antibody (JP-A-2008-120824 and JP-A-2001-112472) have heretofore been developed. However, the HPLC method is associated with defects in that measurement of one sample takes time and multiple samples cannot be analyzed simultaneously, an expensive apparatus is necessary and the like. The immunological measurement method is also associated with defects in that substrate specificity is low and determination of DPD deficiency is difficult, it is costly and the like.
As a DPD activity measurement method other than quantification of uracil, a method of directly measuring the DPD activity of peripheral blood mononuclear cells (B. E. Harris, R. Song, S. Soong and R. B. Diasio, Cancer Res. 1990, 50, 197-201), and a method including administering uracil labeled with a radioisotope and measuring the content of metabolized labeled CO2 in the breath (L. K. Mattison, H. Ezzeldin, M. Carpenter, A. Modak, M. R. Johnson and R. B. Diasio, Clin. Cancer Res., 2004, 10, 2652-2658) have been reported. However, they are associated with various problems in that the former does not permit simultaneous analysis of multiple samples since it requires HPLC separation, and the latter uses radioactive substances, may misdiagnose as DPD deficiency due to the influence of other enzymes and the like.
With such background, the DPD activity measurement methods developed heretofore are not used for routine examination in hospitals, and at present, the DPD activity of patient is measured only when a side effect such as nausea and the like or abnormality in blood examination is observed after administration of a fluorinated pyrimidine anti-cancer agent. Therefore, many cases of death have been reported in the world, which were caused by aggravation of side effects even though administration of fluorinated pyrimidine was discontinued after finding DPD deficiency (Tomoyuki Takaba, Jin Moriyama, Tsuyoshi Yokoyama, Shuichiro Matoba, Toshihito Sawada, The Japanese Journal of Gastroenterological Surgery, 2008, vol. 41, pages 2075-2080).
Therefore, the development of a uracil quantification method and a DPD deficiency examination method, which are capable of detecting uracil highly accurately and economically by a convenient method in a short time, has been desired.